1. Field of the Invention
The present invention relates to an eccentric commutator used as a silent call device for a mobile communications apparatus and an improvement in assembly and structure of a compact vibrator motor using the eccentric commutator.
2. Description of the Related Art
Conventionally, as a silent call device for pagers or mobile phones, as shown in FIG. 8, an eccentric weight W formed of tungsten alloy is coupled to an output shaft S of a cylindrical DC motor M. During rotation of the motor M, vibrations are generated due to the difference in centrifugal force of the eccentric weight W.
However, as the above addition of the eccentric weight W to the output shaft S requires a space for rotation of the eccentric weight W in an apparatus such as a pager, there is a limit in designing the apparatus. Also, use of the expensive tungsten alloy increases the production costs.
Thus, the present applicant has suggested a cylindrical coreless vibrator motor in Japanese Patent Application No. Hei 2-309070 and the corresponding U.S. Pat. No. 5,107,155, in which a built-in rotor itself is made eccentric excluding an output shaft. The above motor having no output shaft and no eccentric weight is favorably noticed by the market as there is no limit in design, use thereof is easy and there is no danger during rotation. However, as the motor requires three cylindrical coreless coils, the number of parts or processing steps increases.
In order to make a rotor with an iron core itself vibrate instead of the cylindrical coreless coil type core, the present applicant has suggested removing one of three salient pole type iron cores as disclosed in Japanese Patent Application No. Hei 2-294482. The above two salient pole type iron cores are preferable in the case of a motor such as a massager needing a relatively large amount of output. However, for a portable apparatus such as a portable terminal consuming a low voltage, movement of the center of mass is little and the amount of vibration is insufficient.
Also, as disclosed in U.S. Pat. No. 5,341,057, the present applicant has suggested a compact vibrator motor having an eccentric armature iron core which is formed by arranging a rotor in which three salient poles made of magnetized material are distributed at one side, to face a tetrapolar field magnet having four alternate north and south pole sections. Also, the same technical concept has been disclosed in Japanese Laid-open Patent Application No. Hei 9-261918. However, as the three armature iron cores made of magnetized material are distributed at one side and cogging torque (a force of being absorbed by a field magnet) increases in the case of the motor, the gap of the motor needs to be enlarged and the diameter of the motor itself cannot be reduced.
In the above motor having a built-in type eccentric rotor, as the size of the above motor is reduced, the distance between armature coils decreases. Thus connection of an end portion of the armature coil to the commutator without damage to the armature coil is very difficult. Particularly, when a printed circuit board is used as a flat panel commutator as it is, where the end portion of the armature coil is directly welded thereon, welding of the end portion is not easy because the end portion is easily detached from a printed pattern due to an elastic force of the end portion.
Also, as the commutator itself is generally a balanced circular shape, the number of parts such as an additional eccentricity emphasizing member increases in the built-in type eccentric rotor.
To solve the above problems, it is a first objective of the present invention to provide an eccentric commutator which can realize a vibrator motor with a reduced number of parts. That is, an additional eccentric member is not needed by securing movement of the center of the commutator itself when being used for a vibrator motor.
It is a second objective of the present invention to provide an eccentric commutator in which intensity of a commutator member having a particular shape is secured.
It is a third objective of the present invention to provide a structure of an eccentric commutator in which connection of each end is easy because an end connection portion is separated from an armature coil.
It is a fourth objective of the present invention to provide an eccentric commutator which can receive a shaft as it is.
It is a fifth objective of the present invention to provide a vibrator motor using the above eccentric commutator, which needs less parts and is low in cost.
The above objectives can be achieved by an eccentric commutator made by forming a plurality of commutator pieces on a commutator base member formed as a printed wiring plate, in which high density resin having a specific gravity of 3 or more is added to at least a part of the commutator base member and a shaft receiving portion is simultaneously is provided at the center thereof by making at least the high density resin portion to be eccentric.
It is preferred in the present invention that the high density resin has a specific gravity of 5 through 12 and is provided with a shaft receiving portion having a lubricating component at the central portion thereof.
It is preferred in the present invention that the commutator base member is formed to be a non-circular shape viewed from a plane and is formed by making an extension portion incorporated with the commutator piece to be eccentric.
It is preferred in the present invention that the commutator base member is used to reinforce the high density resin portion.
It is preferred in the present invention that the extension portion incorporated with the commutator piece protrudes from the commutator base member to be a connection terminal portion, and that the connection terminal portion has a notch at a position opposite to the center of mass so as not to overlap the armature coil, when shown in a plane view.
It is preferred in the present invention that the commutator base member exhibits a slipping feature of a dynamic frictional coefficient of 0.4 (1.5 kg/cm2) or less, and has a sliding resin portion having a shaft receiving hole at the center thereof.
The eccentric commutator can be manufactured by forming a plurality of connected commutator base members, each of which is formed of a printed wiring board, collectively setting the connected commutator base members to a mold, and integrally forming the eccentric commutators by making high density resin having a specific gravity of 3.5 or more to be eccentric.
A flat type coreless vibrator motor having the eccentric rotor comprises an eccentric commutator and a plurality of armature coils arranged in the eccentric commutator.
It is preferred in the present invention that the eccentric rotor is formed by arranging integrally a plurality of air-core armature coils by using a position determination guide arranged in the eccentric commutator.
According to the invention, a compact vibrator motor which does not need an additional eccentric member can be provided, as the center of mass can be moved in the commutator itself.
According to the invention, the amount of eccentricity can be increased.
According to the invention, an eccentric commutator having strength is possible.
According to the invention, as the connection portion is separated from the armature coil, soldering can be easily performed.
According to the invention, a special shaft receiving portion is not needed.
According to the invention, an eccentric commutator can be manufactured in mass and inexpensively.
According to the invention, an eccentric rotor can be easily configured.
According to the invention, the position of an air-core armature coil can be accurately determined and the air-core armature coil can be firmly fixed.